This invention relates generally to the manufacture of kinescopes such as for color television receivers or computer displays and particularly to the measurement of the offset between the faceplate panel and funnel of such a kinescope.
The picture tube, or kinescope, for a color television receiver or computer display is composed of a faceplate panel and a funnel which are fritted together along mating sealing edges. A frit material is placed on the sealing edge of either the panel or the funnel. The panel and funnel are placed together and are put into a carrier which conveys them into an oven. The carrier includes reference members which accurately position the funnel and the panel relative to one another so that the sealing edges of the two elements properly mate along a smooth seal line. The carrier is moved by a conveyor system through the oven and the frit material vitrifies to permanently join the panel and funnel. Typically kinescopes are substantially rectangular with slightly rounder sides. The proper operation of the kinescopes requires accurate alignment of the panel and funnel along the major axis. For this the funnel is provided with a reference pad on the major axis. The position of the panel with respect to the reference pad is thus indicative of whether or not the panel and funnel are properly aligned. Thus, an offset in either direction along the major axis which exceeds a predetermined maximum indicates an unacceptable kinescope. Additionally, because the carrier is used to align the panel and funnel an excessive offset frequently is indicative of a damaged or improperly calibrated carrier. The carrier thus should be repaired or recalibrated to avoid producing additional rejects. For these reasons, there is a need for a device fqr automatically and accurately measuring the offset between the funnel and panel of a kinescope to verify that the offset does not exceed a predetermined maximum. The instant invention fulfills this need by the provision of a device for measuring such offset and for providing a reject signal which can be used to identify the kinescope as a reject and the carrier as potentially damaged or miscalibrated.